JP2008153323A - Laser oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser oscillator for achieving high quality processing. <P>SOLUTION: The laser oscillator includes an optical resonator with mirrors at both ends thereof, a laser medium arranged on an optical route confined within the optical resonator, a Q switch, a loss adjusting element, and an exciting light source for exciting the laser medium. In this laser oscillator, the laser medium is excited with the exciting light source to amplify the light reciprocating within the optical resonator through stimulated emission, the Q switch changes the Q value of the optical resonator, and the loss adjusting element changes amount of attenuation in intensity of the light reciprocating within the optical resonator. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser oscillator including a Q switch.

  In the Q-switch solid-state laser oscillator, the rise time of the emitted pulsed laser beam is determined by the rise time of the Q switch, and the fall time is determined by energy loss in the resonator. That is, the pulse width of the emitted pulsed laser beam is determined by the rise time of the Q switch and the energy loss inside the resonator.

  The energy loss in the resonator is often caused by factors that cannot be controlled. For this reason, the pulse width of the pulse laser beam emitted from the Q-switched solid-state laser oscillator has not only individual differences between the laser oscillators, but also a single unit. Even in the laser oscillator, a change occurs due to aging and the like, and for example, the pulse width generally decreases with aging.

  When the pulse width of the pulse laser beam changes, the processing quality also changes. For example, in laser annealing, changes in pulse width affect the penetration depth and recrystallization of the workpiece.

  Therefore, a technique for keeping the pulse width constant is desired.

  An invention of a pulse width adjusting solid-state laser using a Q switch that can achieve setting of a pulse width in units of μs is disclosed (for example, see Patent Document 1).

  In addition, there is a disclosure of an invention of a pulse laser oscillator that generates two types of pulse laser beams having different peak outputs, pulse widths, and pulse generation cycles (see, for example, Patent Document 2).

JP 2001-189513 A JP 2006-73646 A

  An object of the present invention is to provide a laser oscillator capable of realizing high quality processing.

  According to one aspect of the present invention, an optical resonator in which mirrors are disposed at both ends, a laser medium, a Q switch, and a loss adjustment element disposed on a light path confined in the optical resonator, An excitation light source for exciting a laser medium, wherein the laser medium is excited by the excitation light source to amplify light reciprocating in the optical resonator by stimulated emission, and the Q switch includes the optical resonator A laser oscillator is provided in which the loss adjustment element changes an attenuation amount of light intensity of light traveling back and forth in the optical resonator.

  According to another aspect of the present invention, an optical resonator having mirrors disposed at both ends, a laser medium and a Q switch disposed on a light path confined in the optical resonator, and the laser medium The laser medium is excited by the excitation light source and amplifies light reciprocating in the optical resonator by stimulated emission, the Q switch includes an acoustooptic device, and the acoustic light source. There is provided a laser oscillator including an incident angle adjuster that adjusts an incident angle of the light incident on an optical element.

  Furthermore, according to another aspect of the present invention, an optical resonator having mirrors disposed at both ends, a laser medium and a Q switch disposed on a light path confined in the optical resonator, and the laser medium An excitation light source that excites and a control device that controls application and non-application of a voltage to the Q switch; and the laser medium is excited by the excitation light source to reciprocate light that reciprocates in the optical resonator. Amplifying by stimulated emission, the Q switch includes an electro-optic modulation element and an element that changes a Q value of the optical resonator depending on a polarization state on which light emitted from the electro-optic modulation element enters. The control device is provided with a laser oscillator that applies a voltage different from a voltage for rotating the polarization direction of linearly polarized light by 90 ° to the electro-optic modulation element.

  ADVANTAGE OF THE INVENTION According to this invention, the laser oscillator which can implement | achieve high quality processing can be provided.

  FIG. 1 is a schematic diagram showing a laser oscillator according to a first embodiment.

  The laser oscillator according to the first embodiment is disposed in the housing 17 so as to face the end mirror 10 and the output coupler 15 constituting both end mirrors of the optical resonator, and on the light path confined in the optical resonator. Laser medium 11, Q switch 12, loss adjusting element 13, and shutter 14. The pumping light source 16, the LD driver 18, the RF driver 19, and the controller 20 are included.

  The end mirror 10 is, for example, a total reflection mirror, and the output coupler 15 is an output mirror disposed on the laser output side. For example, the output coupler 15 reflects 96% of light and transmits 4% of light.

The laser medium 11 is an Nd: YAG rod, for example, and its central axis is the optical axis of the optical system composed of the end mirror 10 and the output coupler 15 (the optical axis of light confined in the optical resonator). Match. As the laser medium 11, an Nd: YLF rod, a YVO ₄ rod, or the like may be used.

  The excitation light source 16 includes, for example, a semiconductor laser (Laser Diode; LD). The laser beam emitted from the semiconductor laser (LD) is condensed by, for example, a condenser lens and irradiated on the laser medium 11 in order to improve excitation efficiency. A flash lamp may be used in place of the semiconductor laser (LD).

  The LD driver 18 generates an electrical signal that controls light emission of the semiconductor laser (LD) and transmits the electrical signal to the excitation light source 16.

  The laser medium 11 is excited by excitation light from the excitation light source 16 and amplifies light that reciprocates in the optical resonator by stimulated emission.

The Q switch 12 includes, for example, an acousto-optic element, and changes the Q value of the optical resonator.
A high-frequency electrical signal RF generated by the RF driver 19 is applied to the acoustooptic device. Ultrasonic waves are generated inside the acoustooptic device to which the electrical signal RF is applied, and this acts as a diffraction grating to deflect and emit part of the incident light. Application of the electrical signal RF changes the Q value of the optical resonator, and energy is stored in the laser medium 11. When the application of the electric signal RF is canceled, the Q switch 12 is opened, and a Q switch laser beam (Nd: YAG laser fundamental wavelength: 1064 nm) is emitted from the output coupler 15 side.
Control of the emission of the Q-switched laser beam can be performed by opening and closing the shutter 14. The shutter 14 is opened and closed by a control signal from the controller 20.

  The controller 20 transmits control signals to the shutter 14 and also sends control signals to the LD driver 18 and the RF driver 19 to emit light from the excitation light source 16 (semiconductor laser (LD)) and the Q switch 12 (acoustooptic device). Controls the deflection of the laser beam at.

  The laser oscillator according to the first embodiment is characterized in that, for example, a plurality of loss adjusting elements 13 are arranged on the optical path of the beam between the end mirror 10 and the output coupler 15.

  The loss adjusting element 13 is a parallel plane substrate made of synthetic quartz, for example. The substrate surface (beam entrance / exit surface) may be subjected to antireflection treatment such as AR coating (Anti Reflection Coating) as necessary. For example, the amount of transmitted light (light intensity) can be attenuated by about 0.1% with one loss adjusting element 13 (AR-coated synthetic quartz substrate). In order to prevent parasitic oscillation, the loss adjusting element 13 is relative to the optical axis of light reciprocating in the optical resonator (relative to the optical axis of the optical system composed of the end mirror 10 and the output coupler 15). The substrate surface is not arranged vertically, but is inclined at an angle of several degrees. In addition, a compensator is inserted on the optical axis of the beam in order to correct the optical axis shift caused by the loss adjusting element 13 being arranged obliquely.

  By inserting the loss adjusting element 13 inside the optical resonator, the loss of the optical resonator and the pulse width of the emitted laser beam can be controlled. For example, the loss of the optical resonator is controlled by changing the number of the loss adjusting elements 13 to be inserted (the amount of attenuation of the light intensity of light reciprocating in the optical resonator is changed) to adjust the pulse width.

  For example, when the power loss of the beam generated inside the optical resonator increases with time, the loss in the optical resonator is kept constant by reducing the number of inserted loss adjusting elements 13. By doing so, the pulse width of the emitted pulse laser beam can be kept constant, and stable and high-quality processing can be realized.

  In addition, a beam power adjusting device such as a variable attenuator can be arranged on the optical path of the laser beam emitted from the optical resonator to keep the laser beam power constant.

  In the first embodiment, a synthetic quartz substrate coated with AR coating is used as the loss adjusting element 13 for changing the attenuation of the light intensity of light reciprocating in the optical resonator. It can also be used. An optical resonator in which an end mirror 10 and an output coupler 15 are arranged on an optical path of incident / reflected light of a reflectivity variable mirror, and the end mirror 10 and the output coupler 15 are both end mirrors via the reflectivity variable mirror. Configure. When using a mirror with variable reflectivity, no compensator is required.

  FIG. 2 is a schematic diagram showing a laser oscillator according to the second embodiment.

  Unlike the first embodiment, the second embodiment does not include a loss adjustment element. The loss adjustment of the beam intensity in the optical resonator is performed by devising the configuration of the Q switch 12.

  The Q switch 12 in the second embodiment includes an acousto-optic element 12a and an incident angle adjuster 12b. The incident angle adjuster 12b can adjust the position of the acoustooptic element 12a and change the incident angle (incident direction) of the beam incident on the acoustooptic element 12a.

  The light transmittance of the acoustooptic element 12a is maximized when the incident angle of the beam with respect to the acoustooptic element 12a coincides with the Bragg angle. When the incident angle (incident direction) deviates from the position, the acoustooptic element 12a. The light transmittance is low. Accordingly, the loss can be adjusted by changing the position of the acoustooptic device 12a relative to the incident beam by the incident angle adjuster 12b and shifting the incident angle of the beam from the Bragg angle.

  Even when a configuration that does not include the incident angle adjuster 12b is employed, the same effect can be achieved by controlling the power of the high-frequency electrical signal RF applied to the acoustooptic device 12a.

  FIG. 3 is a schematic view showing a laser oscillator according to the third embodiment.

  The third embodiment is different from the second embodiment in that the Q switch 12 includes an electro-optic modulation element 12c and a polarizer 12d.

  The driver 21 receives a control signal from the controller 20 and applies a voltage to the electro-optic modulation element 12c. The electro-optic modulation element 12c rotates and emits the polarization plane of incident light by an angle corresponding to the applied voltage value.

  The polarizer 12d transmits the P-polarized component with respect to the light incident surface of the polarizer 12d and reflects the S-polarized component.

  Conventionally, a voltage V (voltage that rotates the polarization direction of linearly polarized light by 90 °) V is applied to the electro-optic modulation element 12c as a P wave incident on the electro-optic modulation element 12c.

In the third embodiment, the controller 20 performs control to apply a voltage (a voltage deviating from the voltage V) V ± ΔV to the electro-optic modulation element 12c via the driver 21. Do.
By applying a voltage V ± ΔV to the electro-optic modulation element 12c, the state of linearly polarized light (S wave) emitted from the electro-optic modulation element 12c is deteriorated (a beam emitted from the electro-optic modulation element 12c and incident on the polarizer 12d). Can be elliptically polarized). By doing so, the gain in the resonator can be changed and the loss can be adjusted.
In the third embodiment, the polarizer is used as the element that changes the Q value of the optical resonator depending on the polarization state. However, for example, a polarization beam splitter can also be used.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

It is the schematic which shows the laser oscillator by a 1st Example. It is the schematic which shows the laser oscillator by a 2nd Example. It is the schematic which shows the laser oscillator by a 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 End mirror 11 Laser medium 12 Q switch 12a Acousto-optic device 12b Incident angle adjuster 12c Electro-optic modulation device 12d Polarizer 13 Loss adjustment device 14 Shutter 15 Output coupler 16 Excitation light source 17 Housing 18 LD driver 19 RF driver 20 Controller 21 driver

Claims (5)

An optical resonator with mirrors at both ends;
A laser medium, a Q switch, and a loss adjustment element disposed on a path of light confined in the optical resonator;
An excitation light source for exciting the laser medium,
The laser medium is excited by the excitation light source and amplifies the light reciprocating in the optical resonator by stimulated emission,
The Q switch changes a Q value of the optical resonator,
The loss adjustment element is a laser oscillator that changes an attenuation amount of light intensity of light reciprocating in the optical resonator.   2. The laser oscillator according to claim 1, wherein the loss adjusting element is a flat substrate disposed obliquely with respect to an optical axis of light reciprocating in the optical resonator.   Further, the optical axis is shifted on the optical path of light traveling back and forth in the optical resonator, and the plane substrate is disposed obliquely with respect to the optical axis of light traveling back and forth in the optical resonator. The laser oscillator according to claim 2, further comprising a compensator for correcting the above. An optical resonator with mirrors at both ends;
A laser medium and a Q switch disposed on a path of light confined in the optical resonator;
An excitation light source for exciting the laser medium,
The laser medium is excited by the excitation light source and amplifies the light reciprocating in the optical resonator by stimulated emission,
The Q switch is a laser oscillator including an acoustooptic device and an incident angle adjuster that adjusts an incident angle of the light incident on the acoustooptic device. An optical resonator with mirrors at both ends;
A laser medium and a Q switch disposed on a path of light confined in the optical resonator;
An excitation light source for exciting the laser medium;
A control device for controlling application and non-application of voltage to the Q switch,
The laser medium is excited by the excitation light source and amplifies the light reciprocating in the optical resonator by stimulated emission,
The Q switch includes an electro-optic modulation element and an element that changes a Q value of the optical resonator depending on a polarization state on which light emitted from the electro-optic modulation element enters.
The control device is a laser oscillator that applies a voltage different from a voltage for rotating the polarization direction of linearly polarized light by 90 ° to the electro-optic modulation element.

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